A taxonomy for brainstem cavernous malformations: subtypes of midbrain lesions

Area of Science:

• Neurosurgery
• Neurology
• Radiology

Background:

• Brainstem cavernous malformations (BSCMs) are complex lesions with variable presentation.
• Existing anatomical taxonomy aids clinical decisions for brain arteriovenous malformations.
• A novel taxonomy for midbrain BSCMs is proposed based on clinical presentation and MRI location.

Purpose of the Study:

• To develop and validate a novel taxonomy for midbrain cavernous malformations.
• To correlate subtypes with clinical presentation, surgical approach, and neurological outcomes.
• To enhance diagnostic acumen and surgical strategy for BSCMs.

Main Methods:

• Developed a taxonomy system applied to a 30-year, 2-surgeon experience (1990-2019).
• Subtyped 151 midbrain BSCMs based on preoperative MRI: interpeduncular, peduncular, tegmental, quadrigeminal, and periaqueductal.
• Assessed neurological outcomes using modified Rankin Scale (mRS), comparing characteristics and outcomes among subtypes.

Main Results:

• Each subtype presented with distinct neurological symptoms (e.g., oculomotor nerve palsy, hemiparesis, Parinaud syndrome, hydrocephalus).
• Specific surgical approaches were preferred for each subtype (>90% of cases).
• Favorable outcomes (mRS ≤ 2) were achieved in 80.9% of patients, with no significant difference between subtypes.

Conclusions:

• The proposed taxonomy effectively guides surgical approach selection and resection strategy for midbrain BSCMs.
• This classification enhances bedside diagnostic accuracy and clinical communication.
• The taxonomy has the potential to improve patient outcomes for midbrain cavernous malformations.